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Volume 80, Issue 5
Displaying 1-6 of 6 articles from this issue
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Overview
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—A new technology characterized by radical propagation in giant molecules—Jin Mizuguchi, Shigeru Suzuki, Masahiko Kaneko, Hiroo Takahashi2016 Volume 80 Issue 5 Pages 297-308
Published: 2016
Released on J-STAGE: April 25, 2016
Advance online publication: March 11, 2016JOURNAL FREE ACCESSThermal activation of semiconductors (TASC) is our novel technology characterized by radical propagation in giant molecules, allowing us to decompose any polymers, in an instant, into H2O and CO2. The present phenomenon has successfully been applied to complete decomposition of VOC (volatile organic compound), or to elimination of polymer matrix in composites to recover valuables, for example, decomposition and recovery of FRPs (fiber reinforced plastic), repair of partially damaged FRPs, reclaim of rare-earth powder from resin-bonded magnets, disassembly and recycling of solar panels and laminated glass. The TASC technology dates back to our accidental finding that significant oxidative properties appear in semiconductors when heated at about 350-500 ℃ while quite inactive at room temperature. The oxidative effect (i.e. removal of bonded electrons) has been interpreted as arising from thermally generated defect electrons (“hole”) formed in the valence band of semiconductors. This triggers the decomposition of polymers by creating unstable radicals. Then, the radicals propagate, just like a domino effect or chain reaction, throughout the polymer to make the whole polymer unstable, resulting in the fragmentation of the giant molecule into small pieces such as ethylene and propane. Finally, the fragmented molecules react with oxygen in air to give H2O and CO2 (i.e. complete combustion). This process caused by radical propagation is compared to the reverse reaction of “radical polymerization”. The present overview describes the recent advances in TASC technology with major focus on the disassembly and recycling of solar panels and laminated glass.
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Regular Article
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Motoaki Morita, Osamu Umezawa2016 Volume 80 Issue 5 Pages 309-316
Published: 2016
Released on J-STAGE: April 25, 2016
Advance online publication: February 12, 2016JOURNAL FREE ACCESSThe microstructure of scale adhered to the inner wall of elbow steel pipe, in which the gushing hot spring water was flowed for 3.5 months at a geothermal plant in Obama-cho, Unzen-shi, Nagasaki, Japan, was analyzed. The adhesion substance consisted of four layers, that were amorphous magnesium silicate, aragonite, amorphous magnesium silicate and corrosion product of iron on the carbon steel from top to bottom. The corrosion product fully covered the steel surface. The magnesium silicate with the thickness of 1-2 mm was initially generated as adhesion substance on the corrosion product. The layer thickness of aragonite, orthorhombic calcium carbonate (λ-CaCO3), was 15-70 mm. The elements of calcium carbonate such as carbon, oxygen and calcium were solved in the magnesium silicate, and the calcium carbonate with massive and/or stratiform was precipitated there. The chemical contents in the magnesium silicate layers on both the top side and the bottom one were the almost the same. Therefore, the precipitation of aragonite and its growth in the magnesium silicate may form the aragonite layer which showed a columnar structure along the heat flux direction.
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Yusuke Fukada, Naoki Ide, Yoichi Nishino2016 Volume 80 Issue 5 Pages 317-320
Published: 2016
Released on J-STAGE: April 25, 2016
JOURNAL FREE ACCESSThe deformation behavior of fine-grained Heusler-type Fe2VAl alloys (average grain diameter d=14, 2.0, 1.4 and 0.4 μm) made by pulse current sintering (PCS) has been investigated in comparison with the arc-melted alloys with d=130 μm. The yield stress of the Fe2VAl alloys at 300 K increases as the grain size decreases, following the Hall-Petch relationship except for d=0.4 μm. An anomalous increase in the yield stress with increasing temperature can be observed for d=14 and 130 μm, whereas the yield stress peak disappears for d≤2.0 μm. The yield stress decreases at a lower temperature for finer grains, which occurs in parallel with a steep rise in the strain rate sensitivity exponent m. The m value for d=2.0 μm reaches the maximum of 0.32 at 1123 K, and the temperature is almost 200 K lower than that for d=130 μm. The decrease in the yield stress can be explained by a lower temperature superplasticity for finer grained alloys.
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Sagiri Takase, Chisato Kubo, Masae Kanda, Yoshitake Nishi2016 Volume 80 Issue 5 Pages 321-325
Published: 2016
Released on J-STAGE: April 25, 2016
Advance online publication: March 18, 2016JOURNAL FREE ACCESS2-layer laminated sheets (PU/PET) with Polyurethane (PU) and Polyethylene Terephthalate (PET) were prepared by an adhesion method of a double-step treatment consisting of applying low dose (≦0.43 MGy) homogeneous low energy electron beam irradiation (HLEBI) prior to hot-press under 3 MPa and 348 K. Although the adhesion of the PU/PET was observed with a weak hot-press without HLEBI, the adhesion raised the bonding forces as evidenced by using the adhesive energy of peeling resistance (oEp). Based on the 3-parameter Weibull equation, the lowest oEp value at peeling probability (Pp) of zero (Es) could be estimated. An increasing trend in Es occurred by the double-step treatment applying HLEBI up to 0.43 MGy reaching a maximum at 0.87 kJ•m−1, improving the safety level without radiation damage. When HLEBI cut the chemical bonds in PU and generated terminated atoms with dangling bonds, they probably induced the chemical bonding. Thus, increasing adhesion force between the laminated sheets could be explained.
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Masahiro Kitada, Yohsei Kohzuma, Toru Tateishi2016 Volume 80 Issue 5 Pages 326-333
Published: 2016
Released on J-STAGE: April 25, 2016
JOURNAL FREE ACCESSThe microstructure of the stucco surface containing Pb of the Takamatsuzuka tumulus, constructed in the 7th-8th century, has been investigated. The purpose of this research is to clarify the existing condition of Pb near the stucco surface. A spectro-reflectometer, a scanning electron microscope, and a transmission electron microscope are used to analyze the microstructure. The surface of the specimen consists of three colored areas; white, dull ocher, and ocher. Although the absorption edges of the white stucco CaCO3 and ocher area on the surface are approximately 2.8 and 2.0 eV respectively, the dull ocher area does not show the absorption edge. The latter absorption edge is caused by Fe ion contained in the surface layer. The dull ocher area is rich in Pb. The surface layer consists of fine lead carbonate grains with a size of 100-200 nm. On the layer under the surface layer, CaCO3 grains containing lead oxide precipitates, that is, Pb3O4 and Pb2O3, and CaCO3 grains containing Pb atoms are observed. The size of the lead oxide in CaCO3 is 10-500 nm. These grains are formed by the reaction between the lead carbonate and the CaCO3 matrix. It is thought that the lead carbonate is coated on the stucco.
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Kazutaka Fukuda, Yuta Koyanagi, Masayuki Tsushida, Hiromoto Kitahara, ...2016 Volume 80 Issue 5 Pages 334-339
Published: 2016
Released on J-STAGE: April 25, 2016
JOURNAL FREE ACCESSWith a hexagonal close packed structure, magnesium has many slip systems. Pure shear tests were carried out to evaluate their critical resolved shear stresses (CRSS). As a result, the CRSS for the basal slip was 0.7 MPa, and it was close to conventional values. When the shear stress of 40 MPa was applied in parallel to the prismatic plane, the {1012} twin deformation occurred only, and the prismatic slip deformation did not occur.
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